Mexiletine in refractory ventricular arrhythmias

The antiarrhythmic efficacy of mexiletine was evaluated in 28 subjects with recurrent ventricular tachycardia or fibrillation (22 subjects) or with symptomatic complex ventricular ectopy (six subjects). In all, either the arrhythmia was refractory to other drugs, or such therapy was not tolerated. Response to mexiletine was assessed by continuous ECGs, and in five cases by programmed electrical stimulation. Mexiletine abolished the arrhythmia in 12 cases, but was not tolerated long-term in four. Mexiletine was ineffective in 10 subjects. Seven subjects had significant adverse reactions during short-term dosing; in six, mexiletine was discontinued because of adverse effects after the first few doses so efficacy was not evaluated. The most common adverse effects were nausea, tremor, and generalized malaise. We conclude that mexiletine is an effective antiarrhythmic in some patients with life-threatening ventricular arrhythmias refractory to conventional drugs. Adverse effects significantly limit its use.